Process Based Screening Method and Systems Analysis for Pre-Combustion Carbon Capture Using Ionic Liquids

Despite extensive experimental work investigating CO2 solubility in many Ionic Liquids (IL), identifying the most appropriate IL for pre-combustion CO2 capture from a techno-economic perspective, remains highly iterative, due to the significant importance of parameters such as mass transfer efficiency and ease of solvent separation, which are often overlooked during experimental investigations. In this work, a process-based screening method has been developed based on the physical properties of the ILs, the screening method has four main criteria, namely: 1. Mass transfer, 2. Ease of solvent regeneration, 3. CO2 solubility and 4. H2S solubility. Correlations have been developed for each of the four criteria to allow for direct comparison of ILs, and the screening method was used to identify the seven most promising ILs from a database of 295 ILs. The seven ILs where then compared in AspenPlus using a conceptual process containing one absorption, three separation and one compression stage, and a systems analysis was subsequently conducted to compare the ILs using two main criteria, the net power requirement and the cost of CO2 capture. The IL [bmim][NfO] was determined to have the lowest power requirement and lowest CO2 capture cost, whereas [hmim][bti] had the highest values.